Methods for detecting explosives in a range of settings, such as airports, should be highly sensitive, highly specific, and applicable to nonvolatile and thermally unstable substances. Furthermore, they should be fast and not require much sample preparation. Current methods do not measure up; they involve manual sample transfer and are not ideal for detecting nonvolatile or thermally unstable substances.

Takáts et al. show that the recently developed desorption electrospray ionization (DESI) method meets these requirements. An electrospray is directed onto a surface bearing the analyte, and the resulting secondary ions are collected and analyzed by mass spectrometry. Subnanogram amounts of several explosives, including TNT, can be detected on a variety of surfaces such as paper, skin, and metal. Analysis takes just a few seconds, and no sample preparation is required. — JFU